Life's Greatest Miracle

Trace human development from embryo to newborn through the stunning microimagery of photographer Lennart Nilsson.
Airing November 20, 2001 at 9 pm on PBS
Aired November 20, 2001 on PBS

Program Description

A sequel to one of the most popular NOVAs of all time, "Miracle of Life," this Emmy Award-winning program tracks human development from embryo to newborn using the extraordinary microimagery of Swedish photographer Lennart Nilsson.

Transcript

Life's Greatest Miracle

NARRATOR: People do all sorts of things to get attention. And why? It
may be the last thing on his mind, but this man's body is working toward
this.

Whether we're thinking about it or not, our bodies want to make babies. And
our bodies are very good at it. Around the world about 365,000 new babies get
made every day.

But as ordinary as it seems, creating a new human being is no simple feat.
Just think of it. No matter who you are, once upon a time you looked like this.
From a single cell you built a body that has one hundred trillion cells. You
made hundreds of different kinds of tissues and dozens of organs, including a
brain that allows you to do remarkable things.

How did you do it?

Today, we can look closer than ever before: into the womb, into a cell, into
the essence of life itself. Not only can we see what's happening, but now we're
beginning to see how it happens—the forces that build the embryo, the
molecules that drive this remarkable change. We're uncovering the most intimate
details of how life is created, the secrets behind life's greatest
miracle.

NARRATOR: You might think all the people on this beach are just working
on their suntans. But beneath all that sunscreen, under the skin, there's a
frenzy of activity. Without even thinking about it, almost all the adults here
are busy trying to reproduce. They can't help themselves. The urge to procreate
is a fundamental part of life, not just for us but for all life.

Why is this urge so universal? At least some blame can probably go to this:
DNA—the molecule that carries our genes, the chemical instructions for
building our bodies and keeping us alive, all wrapped up in a tiny winding
staircase.

DNA has run the show for more than four billion years for one main reason:
it's very good at making copies of itself. The copies can get passed to a new
generation in a couple of ways.

If you're a bacterium, you might be into cloning—making exact replicas of
yourself. All your descendents have the same DNA and, except for an occasional
mutant, are just like you. It's simple. It works. And genetically it's
extremely boring.

It can also be dangerous.

If humans were all clones, everyone would have the exact same immune system,
and one successful parasite could wipe us all out.

Fortunately, there's sex, the method of choice for 99.9 percent of the
organisms on Earth more complex than bacteria. With sexual reproduction, two
individuals each provide some DNA. Most animals put it into sperm or eggs. If
the two can get together, a new being will be created, one that's different
from its parents and everybody else.

Where there's sex, there's variety. And when it comes to survival of the
fittest, variety has a definite advantage.

All this comes at a price. Sexual reproduction may be popular, but it's also
quite tricky. To get an idea of how tricky, just take a peek inside a man's
testicle.

It's packed with tiny tubes coiled into bundles. Stretched out they could
cover half a mile. Inside all this tubing, the average man is churning out a
thousand new sperm every second. That's about a hundred million new sperm every
day and more than two trillion over a lifetime. And here's the tricky part:
each and every sperm is one of a kind, carrying a unique genetic package.

How is this possible? How can one person produce so many different
combinations of genes? The answer lies in the very special way we make sperm
and eggs, a process called "meiosis."

In almost every cell of your body you have thirty thousand or more different
genes, spread out on very long strands of DNA called "chromosomes." Most cells
have two versions of every gene on a total of 46 chromosomes. Exactly half of
those, 23, came from your mom, and 23 came from your dad. They come in pairs
where the partners are very similar but not quite the same. The only time they
get together is during meiosis.

Here's how it works inside a testicle that's making sperm. First, each
chromosome makes an exact copy of itself, keeping it attached at one point.
They condense, creating an X-shape. Now the chromosome partners get together
and the two, or actually four, will embrace. They cling so closely, big chunks
carrying whole bunches of genes get exchanged between the partners. The cell
then divides twice, each time pulling the pairs apart. The final result is a
sperm or an egg cell with 23 chromosomes, half the normal number.

By itself, the cell is incomplete. But it still holds incredible promise,
because every chromosome now carries a combination of genes that has never
existed before.

All this gene shuffling means that within a single species, there can be an
enormous amount of diversity. And the more diversity, the better the odds are
that someone will survive to create a new generation.

MELINDA TATE IRUEGAS: This is my mom and dad and your mom and
dad.

SERGIO IRUEGUS: And my mom and dad on their wedding day. You definitely
have your mom's eyes. And you can see I definitely have my dad's
eyebrows.

MELINDA TATE IRUEGAS: You do have your dad's eyebrows.

NARRATOR: Melinda Tate Iruegas and her husband, Sergio, are
expecting their first baby.

NARRATOR: Their unborn child carries a mixture of genes not just
from them, but from all their ancestors.

SERGIO IRUEGAS: That's like the spitting image. You look so much like
your mother here.

NARRATOR: But which genes got passed on from whom right now is
anybody's guess.

SERGIO IRUEGAS: Because here you are and this is what our little girl
might look like. I wonder if the baby will have the characteristic eyebrows
that come from my father's side of the family. We call them the Iruegas
eyebrows.

MELINDA TATE IRUEGAS: Or that it won't have my dad's nose.

SERGIO IRUEGAS: Your nose.

MELINDA TATE IRUEGAS: We talked about having children a lot. He would
say, "Five, six." I was like, "Well, let's start with one. Two, maybe
three."

NARRATOR: In their efforts to pass on their genes, Melinda and
Sergio pursued dramatically different strategies. Like most men, Sergio has
been constantly producing sperm since puberty.

But Melinda created all her eggs when she looked like this, a fetus in her
mother's womb. Within a couple of months, she created several million eggs. And
then, the eggs began to die. At the age of 31, Melinda may only have a few
thousand left. But that's okay, because inside an ovary, as opposed to a
testicle, it's quality, not quantity, that counts.

Every month, one of a woman's two ovaries selects an immature egg cell to
lavish with attention. Hundreds of support cells tend the egg, feeding it until
it grows fat. When it's ready, the whole entourage—the egg along with its
helpers—oozes out of the ovary.

Waiting for them is the open end of the Fallopian tube, which leads to the
uterus. Its tentacles capture the egg and pull it inside. The egg is swept
along by muscular contractions of the tube, as well as the constant swaying of
tiny cilia. The egg has everything it needs to start a new life, except for one
thing: DNA from a sperm. And it has to get it fast. If the egg is not
fertilized within a few hours it will die.

With sex, there will always be pressure to meet and impress a mate. When it
comes to actually choosing a partner, there's a lot to consider. For us, it
might be somewhat more complicated than picking the one that smells best, but
there's no doubt that the process can be heavily influenced by chemistry,
natural drugs that flood the brain.

When love is in the air, the body can undergo some dramatic changes. Signals
from the brain speed up the metabolism of glucose. As a result, body
temperature rises, skin sweats, heartbeat and breathing get faster. In a man,
hormones cue blood vessels to relax, allowing the spongy tissue in the penis to
fill with blood. At the height of sexual excitement, millions of sperm are
squeezed out of storage and swept up by fluid gushing from several glands,
including the prostate. The flood carries them into a fifteen-inch-long tube
looping into the abdomen and then out through the penis. It's only about a
teaspoon of liquid, but it typically contains about three hundred million
sperm.

They are immediately in peril. The vagina is acidic, so the sperm must escape
or die. They start to swim, at least some of them. Even in a healthy man, 60
percent of the sperm can be less than perfect. Like this one with two tails.
For these guys, the journey is over.

But what about the rest? What are the chances that one tiny sperm will reach
and fertilize an egg? Sperm are often portrayed as brave little warriors
forging their way through hostile terrain to conquer the egg. Nothing could be
further from the truth.

For every challenge the sperm face, success is, to a great extent, controlled
by the woman's body and even the egg itself.

Take the sperm's first obstacle, the cervix, passageway to the uterus. Most of
the time, it's locked shut, plugged with mucous that keeps bacteria and sperm
out. But for just a few days a month, around ovulation, the mucous becomes
watery and forms tiny channels that guide the sperm through.

Arriving inside the uterus, the sperm are still about six inches away from
their goal—at least a two-day swim.But undulations of the uterine
muscles propel the sperm into the fallopian tube within 30 minutes.

Even a sperm that reaches the tube in record time has no guarantee of
fertilizing an egg. There may be no egg there. Ovulation could still be days
away.

It's the slowpokes, caught up in the cilia lining the tube, who may have a
better chance. It's probably here that chemicals in the woman's body alter the
sperm's outer coating. Only those sperm that are altered can get a date with
the egg. The sperm are released gradually, over the course of a few days, so at
any given time only a couple hundred sperm will move on.

If all goes well, then farther up the tube they'll find the egg. But it's
heavily chaperoned by support cells. And the chaperones are picky. Only some of
the sperm are let through.

Those who make it will face yet another challenge. Underneath the cloud of
cells, the egg itself is encased in a thick protein shell, called the "zona."
To fertilize the egg, the sperm must break through the zona. But even the
strongest can't do it by brute force alone. The egg demands a proper
introduction. Proteins protruding from the sperm's cap must hook up precisely
with a set of proteins on the egg's surface. If they match, the sperm is held
fast and undergoes a dramatic transformation. It sheds its outer coating,
releasing powerful enzymes that dissolve a hole in the zona, allowing the sperm
to push its way through.

The final hurdle passed, the sperm still does not thrust its way into the egg
itself. Rather, the membranes of the two cells fuse, and the egg draws the
entire contents of the sperm inside.

MELINDA TATE IRUEGAS: I don't know. We weren't being as careful as we
should have been. And October came around and I was a day late. And actually I
was having some other problems with my wrist. And we went to the doctor and the
doctor had asked me...he's like, "Well, are you pregnant?" You know, because he
wanted to do an x-ray of my wrist.

SERGIO IRUEGAS: Yeah.

MELINDA TATE IRUEGAS: And I said, "No." And then I thought about it and
I was like, "Well, I don't know." I decided that I better check this out. And
sure enough, it was positive. And when he came home, I was like...

SERGIO IRUEGAS: I could tell she had something to tell me.

MELINDA TATE IRUEGAS: And I was like, "Well you better sit down."

SERGIO IRUEGAS: It was something that we had discussed...

MELINDA TATE IRUEGAS: Yeah.

SERGIO IRUEGAS: ...but hadn't anticipated until about two more years
down the road. So when she told me...yeah...I was ecstatic.

MELINDA TATE IRUEGAS: We were ready. We were definitely ready even if it
was a little early.

NARRATOR: Ready or not, once sperm and egg get together they have their
own agenda: to create a viable embryo. Their chances aren't great. It's
estimated that more than 50 percent of all fertilized eggs fail to develop. If
it's going to survive, the egg has a lot of work to do.

First, it orders the zona to lock out all other sperm. And then the egg must
finish meiosis, expelling half of its chromosomes into this tiny pouch, called
a "polar body." With the door closed behind it, the single sperm already inside
releases its precious cargo.

The sperm's 23 chromosomes stretch out in the roomy, welcoming egg. The
chromosomes of sperm and egg approach each other and then the cell
divides.

Since the moment the sperm entered the egg, 24 hours have passed. All this
time the fertilized egg is moving down the fallopian tube toward the uterus.
Every few hours, the cells divide. Four...eight...sixteen...gradually creating
the building blocks needed to construct an embryo.

On rare occasions, the tiny cluster of cells splits into two groups and
creates two embryos—identical twins. But most of the time the cells stick
together. They must complete just the right number of cell divisions before
they arrive in the uterus about five days after fertilization. What started as
a large single cell has divided into just over a hundred much smaller cells,
but they're still trapped within the hard shell of the zona.

Now called a "blastocyst," the bundle of cells must do two things to survive:
break out of the zona and find a source of nourishment. At the beginning of the
sixth day, it orchestrates an escape. It releases an enzyme that eats through
the zona, and the ball of cells squeezes out. Free at last, the blastocyst
lands on the blood-rich lining of the mother's uterus. It has just passed one
hurdle, but is immediately presented with another.

For in fact it is now in very grave danger. Stripped of its protective
coating, the blastocyst could be attacked by the mother's immune system as a
foreign invader. White blood cells would swarm in to devour it. In its own
self-defense, the ball of cells produces several chemicals that suppress the
mother's immune system inside the uterus, in effect, convincing the mother to
treat it like a welcome guest.

Then it is free to get to work. Searching for food and oxygen, cells from the
blastocyst reach down and burrow into the surrounding tissue. Eventually, they
pull the entire bundle down into the uterine lining. And sooner or later, the
mother will notice.

MELINDA TATE IRUEGAS: Even brushing my teeth would make me...the minty
flavor was just, like, gross. And it made me feel nauseous. And I would
get up and I would try to eat something. And if it...anything smelled off
slightly, then it was...it made me nauseous.

SERGIO IRUEGAS: My mother has told me stories of how my father had gone
through morning sickness. And of course that never really registered until the
first time it started happening to me.

MELINDA TATE IRUEGAS: He literally got...he would get really, really
nauseous and upset, and actually get physically ill sometimes.

SERGIO IRUEGAS: There was a couple of times when that...well, more than
a couple of times when that actually happened.

NARRATOR: Not everybody gets morning sickness. Sometimes months
can go by before the mother gets any sense of the drama unfolding within her
body.

One milestone event takes place just two weeks after conception, when the
blastocyst is about the size of a poppy seed. This is the moment when the cells
start to organize themselves into an embryo. The process is called
"gastrulation."

With animals like frogs, whose embryos develop inside transparent eggs, it's
easy to see it in action. After the egg becomes a hollow ball of many cells,
some cells dive into the center, forming layers which will go on to develop
into different organs.

In humans, gastrulation happens deep inside the mother's uterine lining, so it
can't be photographed. But we think it works something like this:the
blastocyst creates two oblong bubbles, one on top of the other. Sandwiched
between them is a thin layer of cells. These are the cells which one day may
become a baby. At the beginning of gastrulation, some cells begin moving toward
the center. Then they dive downwards, creating a new, lower layer. More cells
plunge through, squeezing in between, forming a third. The cells in the three
layers may not look different, but for each layer, a very different future lies
ahead.

The lower cells are destined to form structures like the lungs, liver, and the
lining of the digestive tract. The middle layer will form the heart, muscles,
bones and blood. And the top layer will create the nervous system, including
the spinal cord and the brain, as well as an outer covering of skin, and
eventually, hair.

This is a human embryo three weeks after fertilization. Less than a tenth of
an inch long, its neural tube, the beginning of the nervous system, is already
in place. A couple of days layer, the top of the tube is bulging outwards on
its way to becoming a brain. With the primitive brain cells exposed, we can see
some are sending feelers, making connections to their neighbors.

As the days pass, changes proceed at a rapid-fire pace throughout the embryo.
Everywhere, cells are multiplying. And they're on the move. Some reach out to
one another, forming blood vessels. A heart begins to beat. As the embryo
lengthens the precursor to the backbone forms. Groups of cells bulge out on the
sides, the beginnings of arms and legs.

This is the embryo four and a half weeks after fertilization. It is only about
a fifth of an inch long. The primitive backbone now curls into a tail, which
will disappear in a few weeks. A large brain is developing, and on the side of
the head: an eye.

How does this happen? How does the embryo transform itself from a blob of
cells into different tissues and organs, and finally into a fully functional
baby?

The secret, of course, lies in your genes—in your DNA. Inside most every cell
in your body, you have the same 46 chromosomes, carrying the same genes. But
not all the cells in your body are the same. Nerve cells, blood cells, cells
lining your intestine, they all look different and they do different
jobs.

That's because in each of these cells different groups of genes are turned on.
And when a gene is turned on, it tells the cell to construct a particular
protein.Proteins are the molecules that build your body—like collagen,
a fiber that makes up much of your skin, tendons, and bones, or keratin in your
hair. Crystallin is the protein that helps make the lens of your eye
clear.

Some proteins do work. Actin and myosin move muscle fibers. Hemoglobin in the
blood carries oxygen from the lungs to the rest of the body.

So when the embryo is developing, how does a cell turn on the right set of
genes and create the right proteins?

Part of the answer seems to be location. Once the basic body plan is
established, with a head on one end, back and front, and left and right sides,
cells seem to know exactly where they are and what they are supposed to become.
This is because cells talk to each other in the form of chemical
messages.

Chemicals in one cell can trigger a reaction in the cell next door that can
spread to the cell's nucleus and turn genes on or off. But what's really going
on in there? How does a gene get turned on?

If all the DNA in a single cell were stretched out, it would be about six feet
long. But it's all wound up very tightly, coiled around balls of protein. For a
gene to be turned on, something has to come in and loosen up the right section.
Then the cell's machinery can latch on and read the DNA, the first step on the
long road to building a protein. Those molecules that can turn genes on play a
key role in every aspect of development, including the process that transforms
the embryo into a boy or a girl.

SERGIO IRUEGAS: We didn't want to know. We wanted to do it, I guess, the
old fashioned way.

MELINDA TATE IRUEGAS: Well, you kind of wanted to know. We did a wedding
ring test, where you took a piece of your hair and the wedding band and you
hold it over the belly and if it moves one way in a circle, then it's a girl;
if it moves in a straight line it's a boy. And that said it was a girl.

And there was a point when we went into the ultrasound where I was waffling.
It was like, "Well, we could look. At this very moment we could look and we
could find out." And I didn't say anything.

SERGIO IRUEGAS: See...but...I was trying to be strong because she was
very adamant about not...

MELINDA TATE IRUEGAS: I said, "No, no, no."

NARRATOR: By the time most ultrasounds are done, around 18 weeks or so,
doctors can sometimes make out the sex. But in the early weeks it's
impossible.

Take a look at a seven-week-old embryo. Try to guess what sex it is. Think
it's a boy? Believe it or not, this is not a penis, at least not yet. It might
become one, but it could just as easily turn into a clitoris, the female sex
organ. At this stage boys and girls look exactly alike.

And not just on the outside. Inside, there are two gonads which could become
testicles or ovaries. And there are two sets of tubes, one in case it's a boy,
the other for a girl.

Of course there is one way to tell the difference: look at the chromosomes in
a cell from the embryo. One pair among the 23 determines sex. An embryo with
two X chromosomes usually becomes a girl. If one of those Xs is a Y, it will
most likely be a boy.

Recently, scientists came up with a good idea of how this works. There are
only about 30 genes on the Y chromosome. One of them is called SRY. This gene
seems to function just once in a lifetime, late in the sixth week of embryonic
development. And only in one place, the gonad.

SRY turns on for a day or two, and the cells churn out its protein. But in
that short time, SRY sets off a chemical chain reaction, turning on other
genes, eventually turning the gonads into testicles, which begin to make
testosterone. Testosterone travels throughout the body. If it reaches the
genitals then the cells here will build a penis.

But if there are two X chromosomes and no Y, different genes get turned on and
the gonads become ovaries. The embryo becomes a baby girl.

This is the power of genes, creating cascades of chemical reactions, defining
the form and function of all the cells in your body.

Sometimes genes send the message to multiply and grow, as with the arm and leg
buds. Sometimes the message is to die, as it is a few days later, to the cells
between the fingers. As the weeks pass, the embryo's genes send billions of
individual messages, constructing new kinds of cells and building organs and
limbs.

Two months after fertilization, the embryo is now called a fetus. Almost all
its organs are in place though they're not working yet. The whole fetus is just
over an inch long and weighs less than a third of an ounce.

Over the next six and half months, it will grow almost four hundred times
larger and prepare for birth. All of this demands a constant supply of
nutrients.

MELINDA TATE IRUEGAS: Serge was a little frustrated 'cause he thought he
was going to be able to go out and get me whatever I craved and whatever I
wanted. And I had the problem of I didn't want anything or crave anything until
I smelled it. And I had to smell my food before I would eat it. I could cook a
whole meal, and if it didn't smell right when I was done with it, you know,
just because I put the wrong spice in there or something, then I couldn't eat
it.

SERGIO IRUEGAS: Well, what about this place here? Let's check out the
menu.

MELINDA TATE IRUEGAS: No.

SERGIO IRUEGAS: No?

MELINDA TATE IRUEGAS: No.

SERGIO IRUEGAS: We would go out on walks sometimes, just around in the
Square.

MELINDA TATE IRUEGAS: No.

SERGIO IRUEGAS: No?

MELINDA TATE IRUEGAS: That's not going to work.

SERGIO IRUEGAS: She would have to smell it first. Just see what caught
her fancy at that time.

MELINDA TATE IRUEGAS: Yeah.

SERGIO IRUEGAS: Yeah?

MELINDA TATE IRUEGAS: Yeah.

SERGIO IRUEGAS: As soon as it did, then that's where we would go.

MELINDA TATE IRUEGAS: And that lasted throughout my entire
pregnancy.

SERGIO IRUEGAS: How is it?

MELINDA TATE IRUEGAS: Garlicky. Yum.

SERGIO IRUEGAS: Baby likes it?

MELINDA TATE IRUEGAS: Yeah. I'm pretty hungry. I'm still like that. I
still really want to smell my food, and if I smell something and I'm just like,
"Oh, I have to have that and I have to have it now."

NARRATOR: It's no surprise that Melinda might be especially hungry. The
fetus she's carrying has only one source for all the raw materials it needs to
grow into a baby: Melinda's blood, which is systematically raided with the help
of the placenta.

The placenta began to form as soon as the blastocyst burrowed into the
mother's uterus, and in the early weeks it dwarfed the embryo. The underside of
the placenta is covered with thousands of tiny projections, called "villi"
which lie in pools of the mother's blood. Without ever mixing the blood of
mother and child, the villi grab oxygen and nutrients. The enriched blood flows
about a foot and a half through the umbilical cord, back to the fetus, whose
heart beats about twice as fast as an adult's.

The heart is one of the few organs that actually work during the earliest
weeks of development. But with other organs, function comes later. With the
eye, although the retina and lens are well-formed by the ninth week, the fetus
doesn't respond to light until the fifth or sixth month.

And the same for the ear. The outer ear quickly takes shape, but the fetus
can't hear yet. Sound conduction relies on the tiny bones of the inner ear, and
most of the bones in the fetus start out as cartilage. By the fourth month,
hard bone can be seen forming in the hand and the leg. Finally, after five
months, the process is complete in the inner ear. And then, the fetus begins to
hear sound.

SERGIO IRUEGAS: I would sing songs, right on her belly, just so that it
could hear my voice and get to know my voice. But there was...

MELINDA TATE IRUEGAS: And what else? And make whale noises.

SERGIO IRUEGAS: Yeah. One of the first times I did that the baby seemed
to move its hand across her belly and kind of touch my lips. Or at least I like
to think it was a hand, saying hello or something.

MELINDA TATE IRUEGAS: And I even play music. You know, I wanted to see
what would happen to what different kinds of music. And, you know, Mozart, you
know...was mellow...kind of made some movements. And then I put salsa music in
and it just started kicking, almost in rhythm. So it was great.

SERGIO IRUEGAS: It had a particular beat that it likes.

MELINDA TATE IRUEGAS: Yes.

NARRATOR: Inside Melinda's belly, a remarkable transformation has taken
place, starting with the moment egg and sperm met. Inside the womb, the first
few weeks are the most dramatic. Later in pregnancy, when the mother's body
seems to be changing the most, life in the womb can appear, well, a bit
uneventful.

All the organ systems are in place, so during the last trimester the fetus's
main job is to grow. But a few crucial events are unfolding beneath the skin.
Fat deposits are forming, building reserves the baby will rely on after birth.
But even more importantly, fat is getting laid down in the brain.

In the sixth month, genes in the brain order the manufacture of a fatty
substance called "myelin," which wraps around the long connections between
brain cells. This fatty covering allows nerve impulses to travel up to 100
times faster, greatly enhancing brainpower. The process will continue for years
after the baby is born.

The brain's hunger for fat in the last trimester puts an enormous strain on
the mother. Over the course of the pregnancy, her body has increased its own
blood supply by about 50 percent, all for the sake of the rapidly growing baby.
But late in pregnancy, the baby's need for fat becomes so great the mother
can't keep up. If it stays inside, the baby will begin to starve. Somehow, it's
got to get out.

MELINDA TATE IRUEGAS: I've only had, like, one anxiety attack. And it
was the moment I was in the bathroom and I just had the thought of, like,
"How's this baby going to get out? I just don't think he's going to make it
out." And I hadn't really thought about it up until that very moment, where I
was just like, "No."

SERGIO IRUEGAS: I love you.

NARRATOR: Giving birth is one of the most amazing experiences a woman
can have. It can also be one of the most painful.

SERGIO IRUEGAS: It's starting to go down.

SHIRLEY TATE (Melinda Tate Iruegas's mother): Remember? Think
about being in that garden.

NARRATOR: Again and again the uterus contracts as the cervix opens up.
The tiny passageway that once allowed the entrance of a single file of sperm
now must widen to about four inches to accommodate a baby's head.

Human births are far more dangerous than those of other mammals or even other
primates. The human brain is three to four times bigger than an ape's brain.
And the pelvis is narrower to allow us to walk upright. A human baby has to go
through considerable contortions to make it through the narrow opening.
Sometimes, there simply is not enough room.

If that happens today, Melinda's baby can be delivered by caesarian section.
But not long ago, before the rise of modern surgery, death was a common outcome
for the baby and the mother.

SERGIO IRUEGAS: I can't help but feel a little guilty that I'm
responsible for this, but it's part of the natural cycle of life. And I just
want to be there in any way that I can to support her through this whole
process.

NARRATOR: Because of the pain and danger of human labor, we regularly give birth in the presence of others. Today,
at 4:25 a.m., Melinda's parents, along with Sergio, will have the privilege of
witnessing firsthand this extraordinary event—life's greatest miracle.

NURSE: Grab it again. All right. That's it. One more time...push it
right down for more...oh good, good, good.

ED TATE (Melinda Tate Iruegas's father): A life! A new life! Look
at that little baby!

SHIRLEY TATE: Oh, a little penis! It's a boy!

SERGIO IRUEGAS: Look at our little boy.

MELINDA TATE IRUEGAS: Hi. I was wondering who you were. You're so
handsome.

SERGIO IRUEGAS: We've been wondering who you were. We've been playing
with you.

National corporate funding for NOVA is provided by Cancer Treatment Centers of America.
Major funding for NOVA is provided by the David H. Koch Fund for Science, the Corporation for Public Broadcasting, and PBS viewers.